16.alpha., 17.alpha.-dialkylated steroids have desirable medicinal properties. See, for example, U.S. Pat. No. 4,686,214; Cairns, et al., J. Chem. Soc., Perkin Trans. I, 1981:2306, and references cited therein.
Previous syntheses of 16.alpha., 17.alpha.-dialkylated steroids have employed a one-step conjugate addition-enolate trapping method to accomplish the addition of the C16 and C17 alkyl groups. For example, see Schaub, et al., J. Med. Chem., 10:789 (1967), and Cairns, et al., J. Chem. Soc., Perkin Trans. I, 1978:1594 and 1976:1558, disclosing alkyl Grignard conjugate addition reaction followed by an alkyl halide quench in a single reaction vessel.
The one-step conjugate addition-enolate trapping method sometimes gives the desired 16.alpha., 17.alpha.-dialkylated steroid in low yield and contaminated with polyalkylated side products. Such side products can be difficult to remove using conventional purification techniques, e.g., recrystallization: Cairns, et al., J. Chem. Soc., Perkin Trans. I, 1981:2306 and 1978:1594.
Alternative methods of preparing 16.alpha., 17.alpha.-dialkylated steroids are desired.